Physical conditioning through regular exercise has long been considered important in achieving and maintaining good overall health. The types of exercise equipment that have been available range from large stationary machines costing thousand of dollars to smaller and simpler items such as jump ropes and small weights. It is generally recognized that building and toning of the muscles in the upper body is effectively achieved by work with free weights. Typically, free weight workouts involve the use of barbells of various sizes.
Although work with free weights is highly popular, it is subject to a number of inherent problems. First, because of the need for different weights for different people and even for different exercises by the same person, a large number of weights are required, and this leads to high costs, storage difficulties and other problems. Safety is a serious problem associated with the use of heavy weights, and injuries are unfortunately rather commonplace. Finally, barbells are normally suitable for use only at home or at an exercise facility because of the difficulty of carrying them from place to place. Thus, free weights are not often used in workouts conducted in offices or during out of town travel.
Various types of exercise machines have been developed, but they are for the most part large stationary devices that are useful only at one location. Resistive force is usually provided by a brake or other friction device that is effective only in one direction. For example, brake resistance devices offer resistance only when a rope is pulled or extended, and the rope retracts freely without offering significant resistance. This is a serious drawback in that physiologists and other fitness experts recognize that muscle development is greatly enhanced if near equal resistance is provided both during extension and retraction (or raising and lowering). Existing devices are further characterized by difficulty in adjusting the resistive force, if it is adjustable at all, and by undue limitations on the range of resistance.